ENERGY SECURITYHydropower Delivers Electricity, Even During Lengthy Droughts
The megadrought in the Southwestern United States is the driest—and longest—in the last 1,200 years, depleting water reservoir levels to critically low levels over the past 22 years. Droughts particularly impact hydroelectric power dams as well as some thermoelectric power plants that require large amounts of water for cooling. But a new report suggests that the relationship between drought and hydroelectric power is more nuanced than it might seem. Drought-strained hydropower sustains 80 percent average power generation capacity.
In 2022, a quick internet search for Lake Mead or Lake Powell returns startling images of drying lake beds and parched land.
The megadrought in the Southwestern United States is the driest—and longest—in the last 1,200 years, depleting water reservoir levels to critically low levels over the past 22 years.
This persistent drought has policymakers and system planners concerned about the reliability of the electric grid under worsening drought conditions and climbing temperatures. Droughts particularly impact hydroelectric power dams as well as some thermoelectric power plants that require large amounts of water for cooling.
But a new report by hydrologists at Pacific Northwest National Laboratory (PNNL) suggests that the relationship between drought and hydroelectric power is more nuanced than it might seem.
To get an accurate picture, PNNL hydrologists combined 20 years’ of annual power generation data from more than 600 hydroelectric power plants with historical precipitation data from eight distinct hydropower climate regions of the Western United States. Each hydropower region faces unique climatic conditions. Unique reservoir operating conditions also add complexity. Using these data, the hydrologists extrapolated hydropower generation as far back as 1900.
They found that, even during the most severe droughts being observed over the last two decades, hydropower has sustained 80 percent of average power generation levels, which equates to about 150 terawatt-hours of renewable electricity—or approximately 20 percent of electricity demand across the West. This flexible power also helps to balance supply and demand in the western grid.
“That’s a noticeable dip—but it’s still a lot of renewable energy,” said Sean Turner, water resources modeler at PNNL and main author of the report.
The PNNL team used machine learning and statistical analysis to categorize hydroelectric plants according to their yearly generating patterns. This analysis revealed distinct hydropower climate regions in the West. For example, hydropower plants west of the Cascades experience different climatic conditions than those to the east, which demonstrates that different climate regions exist in a large river basin like the Columbia River.
“When studying and characterizing drought, the instinct is to look at it from a regional or state level, but state boundaries might not be the most relevant for understanding the impacts of drought on hydropower,” said Turner. “Grouping them by climate conditions leads to a cleaner assessment of the impact of drought on hydropower.”
